Hohner Rhythm 80 Midiinterface

Another old drummer to be midified.

The Hohner Rhythm 80

This was built by Hohner in West-Germany. Lots of early digital internals but 100% analog soundcreation. It has 20 presetrhythms which can be altered in 4 Variations. The 4 variations can be selected/deselected individually and change each 2, 4, 8 or 16 bars. There are 10 Instruments: Bassdrum, low conga (which sounds VERY low, more like a bassdrum), low and high bongo, claves, cowbell, snare, cymbal, highhat (which sounds more like another snaredrum) and maracas. The instruments are built with a double-T-Matrix around just one transistor (like the vermona and most of the drummies from this time). You might have spotted 4 coils on the pcb. They are used to filter the output hihat, cymbal, snare and maracas and NOT for generating fat bassdrums :) Most of the trimpots are for calibrating decay and level.

Cleaning and repairing

Got it for 35 EUR from the bay as 'broken'. Well, broken is ok, but it would be nice if these sellers kept at least the original screws. This on has some special screws which are veeeery long and hold the case together. Half of them are still missing :(

The Hohner has a fade in/fade out function bases around a CA3080. This was burnt by some reason i dont know, after replacing it the machine worked again. Only the maracas were still missing, the cause was a ripped of extremely thin cable from the highpass-coil. Fortunately there still was a bit of the cable in reach, after soldering it back again the maracas also worked. THe output is muted by the ca3080 when the machine is stopped. Cause i want to drive it by midi i removed the 3080 again and shortcut the pins 2 and 6 in the ic-socket to have output permanently open.

Here will be a nice pic from its front.

Midiinterface

Now on to the midiinterface around a Atmega8. As on the vermona the code also is based on Vacolocos Opensource Triggerinterface. Trigger interface was quite easy. Just diodes going to the voices.

Here is a audio demo of the Hohner Rhythm 80